The present invention relates to a hydraulic actuator with wear take-up, for example controlling a clutch of a motor vehicle.
Such an actuator with wear take-up is described, for example, in EP-A-0,310,733.
It comprises a body, in which is formed a blind bore where a first piston slides sealingly under the effect of the pressure of a fluid in a first chamber, a second piston being mounted slideably in a bore made in the first piston and an output rod bearing on said second piston, a second chamber thus being defined between the first and second pistons, a valve means being provided for ensuring hydraulic communication between the first and second chambers when the actuator is at rest and interrupting this communication when the pressure of the fluid in the first chamber is higher than a specific level.
Although operating perfectly, this actuator has the disadvantage of being difficult to bleed, especially in its second chamber.
Moreover, the valve means used in this actuator remains sensitive to the impurities contained in the fluid.
Finally, a central element is always difficult to position and adjust.